The use of constructions comprising ultra-hard and metallic components that are joined together is well known in the art. An example of such can be found in the form of cutting elements comprising an ultra-hard component that is joined to a metallic component. In such cutting element embodiment, the wear or cutting portion is formed from the ultra-hard component and the metallic portion of the cutting element is attached to the wear and/or cutting device. In an example embodiment, the ultra-hard component can be formed from a polycrystalline material such as polycrystalline diamond (PCD), polycrystalline cubic boron nitride (PcBN), or the like, that has a degree of wear and/or abrasion resistance that is greater than that of the metallic component. In particular examples, the ultra-hard component can be formed from PCD that has been formed or treated so that it is substantially free of a catalyst material that is used to form the same and comprises bonded-together diamond crystals.
Conventionally known constructions, comprising such ultra-hard and metallic components, are typically attached to one another using a braze material. The use of a braze material to attach the two components is needed to provide a desired attachment bond as the ultra-hard and metallic components are not themselves capable of forming an adequate bond to one another, e.g., when subjected to high-pressure/high temperature conditions. However, the use of a single-type of braze material to attach the two different components together does not provide a satisfactory degree of attachment for certain demanding wear and/or cutting applications, e.g., where the construction is provided in the form of a cutting element that is attached to a bit used for drilling subterranean formations. This is because a single-type of braze material is not capable of accommodating the vast differences in thermal expansion characteristic for the ultra-hard and metallic component.
Further, using a single-type of braze material makes it very difficult to provide an attachment bond to each of the ultra-hard and metallic components that are equal in strength. Since the ultra-hard and metallic components have different material properties and chemistries, any single-type of braze material that is used to form an attachment therebetween will provide a bond having a compromised degree of bond strength, e.g., where the single-type of braze material can be formulated to provide a strong bond to one component but at the expense of a weakened bond to the other component.
An attempt to address the need to provide an optimized attachment bond within constructions comprising ultra-hard and metallic components has involved the use of an intermediate material interposed between the ultra-hard and metallic components. This attempt involved the formation of a braze joint design that made use of an intermediate material formed from a refractory metal, and use of the same type of braze material interposed between the ultra-hard component and the intermediate material, and interposed between the metallic component and the intermediate material.
While the use of such braze joint design, comprising an intermediate layer and the same type of braze material, has been somewhat helpful in addressing the differences in the thermal expansion characteristic of the ultra-hard and metallic components, and in achieving an improvement in bond strength within the construction, such improvements are still not sufficient to meet the demands of certain wear and/or cutting applications, e.g., when the construction is used as a cutting element in a drill bit for drilling earthen formations where it is subjected to extreme conditions of heat and impact.
It is, therefore, desired that constructions comprising ultra-hard and metallic components be engineered in a manner having an improved braze joint that is specially designed to provide a desired level of ductility to address any differences in expansion characteristics between the ultra-hard and metallic components. It is further desired that such braze joint be capable of providing an optimum level of bond strength within the construction to enable the construction to withstand use in certain demanding wear and/or cutting applications, thereby extending the services life of such constructions when compared to ultra-hard and metallic constructions configured having a conventional braze joint.